1. Field of the Invention
The invention relates generally to a semiconductor power module and, more particularly, the invention relates to a semiconductor power module having an electrically insulating heat sink.
2. Description of Related Technology
Generally speaking, a semiconductor power module is a packaged structure that typically includes a plurality of semiconductor die, which form a power circuit and a control circuit. These semiconductor die are mounted to die pads of a lead frame, which is molded together with a radiating metal plate (commonly referred to as a “heat sink”) using epoxy resin.
As is well known, the power circuit within a semiconductor power module typically includes a power semiconductor element (e.g., a power transistor) that functions as a power switching device and the control circuit typically includes a driving element for driving (i.e., turning on and off) the power semiconductor element and a protection element that protects the power semiconductor element from damage due to over-current conditions, excessive temperatures, etc. In general, the power circuit is structured to radiate a substantial amount of heat because a significant amount of power is controlled and dissipated by the power semiconductor element. On the other hand, the control circuit typically draws small currents and does not dissipate an appreciable amount of power and, as a result, the control circuit typically does not have to be structured to radiate a substantial amount of heat.
As is also generally known, the management of heat generated within a conventional semiconductor power module is complicated by the fact that the power circuit and the control circuit have significantly different heat dissipation requirements. Some developments have attempted to address the differential heat generation characteristics of the power circuit and control circuit within a semiconductor power module while attempting to provide a simple, cost-effective structure. For example, U.S. Pat. No. 5,703,399 generally discloses a semiconductor power module having a lead frame, power and control circuits formed on the lead frame, an electrically conductive heat sink positioned adjacent to the power circuit and a sealer interposed between the heat sink and the lead frame that electrically insulates the heat sink from the lead frame and the circuit components mounted thereto. Unfortunately, the structure disclosed in U.S. Pat. No. 5,703,399 requires a heat sink and a separate insulating layer and further requires that the heat sink be spaced in a uniform and stable manner to the control parasitic electrical effects that are produced as a result of using an electrically conductive material for the heat sink.